Assessing caries lesion activity, whether caries lesions are demineralizing (active) or have stagnated and are now scars of past damage (inactive/arrested), is difficult to determine without longitudinal asessments, especially of non-cavitated lesions (white-spot lesions). This makes clinical decision-making of management interventions very difficult and subjective for the dentist. Therefore, determination of caries lesion activity is one of the main components of caries diagnosis. Activity should be the principal driver in the decision of whether to intervene in the caries process or not to intervene. Incorrect diagnosis may easily result in incorrect treatment decisions, particularly with respect to surgical treatments (restorations). Visual and tactile examinations are the most common and traditional ways to determine caries lesion activity. However, they are subjective assessments. Our long-term goal is to develop an objective and quantitative measure to clinically assess caries lesion activity at the time of examination. The primary goal of this laboratory study is to evaluate lesion activity by objectively assessing the appearance (reflection) and texture (roughness) of demineralizing (and thus, active) caries lesions developed with an active biofilm;and arrested caries lesions (and thus, inactive), in which the demineralization process has been stopped and reversed by means of a remineralization protocol. The secondary goal is to evaluate the validity and reliability of an objective and quantitative means of assessing caries lesion activity using real-time imaging technology [Quantitative Light-induced Fluorescence (QLF)]. Our specific aims are to: 1. Assess the ability of objectively assessed surface reflection (appearance) and roughness (texture) in determining caries lesion activity. We will associate the demineralization (demin) / remineralization (remin) stage of white-spot lesions with objective optical reflectometry (appearance), and objective surface profilometry (roughness). We hypothesize that the active stage (demineralizing) will present less reflection and greater roughness values and the inactive stage will show higher reflection and lower roughness values. 2. Evaluate the use of the objective QLF with dehydration methodology for determination of caries lesion activity. We will also associate the demin/remin stage of white-spot lesions with changes in QLF variables per second ( QLFD) during dehydration. We hypothesize that the QLFD for the active stage will present larger values than that for remineralized/inactive stage. This project is of great significance for the clinical decision-making in the management of dental lesion caries. Particularly, this project will provide clinicians with an objective and quantitative means for determination of caries lesion activity at the time of examination. Activity is what should drive caries interventions;therefore, objective measurement of activity will greatly facilitate clinical decision-making for more effective caries management. PUBLIC HEALTH RELEVANCE: This project is of great significance for the clinical decision-making in the management of dental caries. Particularly, if results are positive, as expected, this project will provide clinicians with an objective and quantitative means for determination of caries activity at the time of examination. Activity is what should drive caries interventions;therefore, objective measurement of activity will greatly facilitate clinical decision-making for more effective caries management.